Merge "Fix preference puts with "null" values."

                    for (Map.Entry<String, Object> e : mModified.entrySet()) {

                        String k = e.getKey();

                        Object v = e.getValue();

                        if (v == this) {  // magic value for a removal mutation

                        // "this" is the magic value for a removal mutation. In addition,

                        // setting a value to "null" for a given key is specified to be

                        // equivalent to calling remove on that key.

                        if (v == this || v == null) {

                            if (!mMap.containsKey(k)) {

                                continue;

                            }

                            mMap.remove(k);

                        } else {

                            boolean isSame = false;

                            if (mMap.containsKey(k)) {

                                Object existingValue = mMap.get(k);

                                if (existingValue != null && existingValue.equals(v)) {